Recently, there has been an increase in demand for higher surface recording density, and in order to respond to this demand, smaller and smaller writing size on a magnetic recording medium may be used. Accordingly, heat fluctuation of magnetization is problematic as a factor of destabilizing a magnetization region of a medium. As a method of solving the problem, a perpendicular magnetic recording method has been used, in which a magnetization signal is recorded in a direction perpendicular to a medium. Even in the perpendicular magnetic recording method, a single pole portion for writing, which generates a recording magnetic field perpendicular to a medium, is reduced in size in order to increase surface recording density, and therefore it is now difficult to generate a sufficiently large perpendicular magnetic field to a medium to induce reversal of magnetization of the recording medium.
To compensate such insufficient writing field strength, a method is given, in which throat height (a range defining width of a writing pole) is reduced, thereby a saturation position of a magnetic field is made close to an air bearing surface to secure a magnetic field strength. However, this leads to a problem that a flare section, which collects magnetic field generated by induction of a coil and guides the magnetic field to the air bearing surface, is located close to an air bearing surface, so that magnetic field leakage occurs from the flare section, and consequently recording width is increased with respect to a geometric width of a single pole for writing.
Thus, some art discloses a method to reduce write blurring by increasing a recording width due to magnetic field leakage, in which a magnetic shield layer is provided around a main pole via a nonmagnetic layer. Jap. Pat. Appl. No. JP-A-2007-87506 and Jap. Pat. Appl. No. JP-A-2007-87551 disclose methods respectively, in which a shield layer combined with a sub pole is provided on a trailing side of a main pole via a nonmagnetic layer to obtain a certain magnetic field gradient while controlling magnetic field leakage on the trailing side. Furthermore, Jap. Pat. Appl. No. JP-A-2005-190518 and Jap. Pat. Appl. No. JP-A-2006-120223 disclose means respectively, wherein shield layers, which are disposed on a trailing side of a main pole and on both sides in a track width direction thereof in a manner of enclosing the main pole from three sides, are used to control write blurring on the trailing side and on both sides in the track width direction.
The magnetic shield disposed via the nonmagnetic layer around the main pole absorbs a magnetic flux that does not need to be written into a recording medium, and defines a magnetic field gradient on a trailing side and defines magnetic track width. However, in the case that the shield has a low element height from an air bearing surface, an adequate shield effect is not obtained, leading to magnetic flux leakage. In the case that the shield has a high element height, amount of magnetic flux to be absorbed by the shield is increased, consequently writing field strength is problematically reduced.
Therefore, it would be beneficial to improve a structure of shields disposed on a trailing side of a main pole and on both sides in a track width direction thereof in a manner of enclosing the main pole from three sides, thereby providing a perpendicular magnetic recording head, in which a high magnetic field gradient is achieved, a shield effect is improved, and recording performance is not degraded.